Granted Patent B2

US 8,382,805 · App. 12/792,072 · Granted Feb 26, 2013

Abstract

Claims (36)

1. A limited angulation bone screw assembly adapted to couple a spinal rod with a vertebra, comprising:

a bone screw ( 10 ) comprising a threaded shaft ( 13 ) and an upper head portion ( 20 ), the upper head portion ( 20 ) being a substantially spherical surface ( 23 ) having flat surfaces ( 18 ) disposed on opposite sides of the upper head portion ( 20 );

a bushing ( 30 ) comprising an upper portion ( 31 ) having a seat ( 33 ) shaped to receive the spinal rod and shoulders ( 38 ) on both sides of the seat, and a lower portion ( 32 ) having a rounded surface ( 35 ) and a pair of opposing flanges ( 43 ) having inner planar surfaces ( 46 ) shaped to slidably couple with the spherical surface ( 23 ) and flat surfaces ( 18 ) of the bone screw ( 10 ) to restrict motion of the bone screw to a single plane; and

a housing ( 50 ) having an upper portion ( 53 ) with a first opening ( 67 ), a lower portion ( 56 ) with a second opening ( 69 ), and a first axis ( 63 ) extending between the upper and lower portions, the upper portion ( 53 ) comprising two spaced apart arms ( 55 ), each arm comprising internal threads ( 61 ) and an internal groove ( 87 ) configured to receive the shoulder ( 38 ) of the bushing ( 30 ), and a U-shaped channel ( 74 ) extending along a second axis transverse to the first axis ( 63 ) adapted to receive the spinal rod, and the second opening ( 69 ) being sized to engage the upper head portion ( 20 ) of the bone screw ( 10 );

wherein the screw is insertable through the first opening ( 67 ) until the threaded shaft ( 13 ) extends through the second opening ( 69 ) and the upper head portion ( 20 ) engages the second opening ( 69 );

wherein the bushing ( 30 ) is insertable through the first opening ( 67 ) in a first orientation with the shoulders ( 38 ) being positioned between the spaced apart arms ( 55 ) until the shoulders ( 38 ) are proximate to the internal grooves ( 87 ), the bushing ( 30 ) then being rotateable to a second orientation with the shoulders ( 38 ) being inserted into the internal grooves ( 87 ) and the bushing seat ( 33 ) aligning with the U-shaped channel ( 74 ); and

wherein the upper head portion ( 20 ) of the screw couples with the lower portion ( 32 ) of the bushing ( 30 ) and permits angulation of the housing ( 50 ) relative to the bone screw ( 10 ) in a plane including the first and second axis,

wherein the bushing ( 30 ) further comprises a groove ( 39 ) adjacent the shoulder ( 38 ) for frictional engagement with the housing.

2. The bone screw assembly of claim 1 , wherein the housing further includes one or more protruding members configured to mate with the groove ( 39 ).

3. The bone screw assembly of claim 1 , wherein prior to insertion through the first opening ( 67 ), the upper head portion ( 20 ) of the screw ( 10 ) is engaged with the lower portion ( 32 ) of the bushing ( 30 ) in the first orientation, and after insertion of both the bushing ( 30 ) and screw ( 10 ) when the shoulders ( 38 ) are proximate the internal grooves ( 87 ), both the bushing ( 30 ) and screw ( 10 ) are rotated to the second orientation.

4. The bone screw assembly of claim 1 , wherein the lower portion ( 32 ) of the bushing ( 30 ) further includes cut-away portions ( 41 ) formed along a bottom circumferential surface ( 42 ).

5. The bone screw assembly of claim 4 , wherein the cut-away portions ( 41 ) are configured to splay over the upper head portion ( 20 ) of the screw ( 10 ) when the bushing ( 30 ) is in a crush locked position.

6. The bone screw assembly of claim 1 , wherein the flat surfaces ( 18 ) includes protrusions ( 23 a ′).

7. The bone screw assembly of claim 1 , further comprising a set screw having external threads configured to engage the internal threads ( 61 ) of the housing ( 50 ).

8. The bone screw assembly of claim 1 , wherein the upper portion ( 53 ) further comprising a recess ( 72 ) configured to interface with an instrument interface.

9. A limited angulation bone screw assembly, comprising:

a bone screw comprising a shaft and a substantially spherical upper head portion having flat surfaces disposed on opposite sides of the upper head portion;

a bushing having an upper portion and a lower portion, the lower portion configured to mate with the upper head portion and the flat surfaces of the bone screw to restrict motion of the bone screw to a single plane and the upper portion having a seat shaped to receive a spinal rod and shoulders on both sides of the seat; and

a housing having an upper portion, a lower portion and a first axis extending between the upper and lower portions, the housing having a first opening at the upper portion, a second opening at the lower portion and internal grooves configured to receive the shoulders of the bushing;

wherein the mated bushing and screw are insertable through the first opening in a first orientation until the shaft extends through the second opening and the shoulders are proximate the internal grooves, the bushing and screw then being rotateable to a second orientation with the shoulders being inserted into the internal grooves, and

wherein the seat aligns with the upper portion of the housing to receive a spinal rod therein along a second axis transverse to the first axis,

wherein the bushing further comprises a groove adjacent the shoulder configured for frictional engagement with the housing.

10. The bone screw assembly of claim 9 , wherein the bushing further comprises a groove adjacent the shoulder and the housing further includes one or more protruding members configured to mate with the groove.

11. The bone screw assembly of claim 9 , wherein the lower portion of the bushing further includes cut-away portions formed along a bottom circumferential surface, the cut-away portions being configured to splay over the upper head portion of the screw when the bushing is in a crush locked position.

12. The bone screw assembly of claim 9 , wherein the flat surfaces includes protrusions.

13. The bone screw assembly of claim 9 , further comprising a set screw having external threads configured to engage internal threads within the housing.

14. The bone screw assembly of claim 9 , wherein the upper portion further comprising a recess configured to interface with an instrument interface.

15. A method of assembling a bone screw assembly capable of uniplanar movement, comprising:

providing a bone screw comprising a shaft and an upper head portion, the upper head portion comprising a spherical surface adjacent first planar surfaces;

providing a bushing, the bushing comprising an upper portion and a lower portion, the upper portion comprising a groove, the lower portion defining a lower rounded surface, the lower portion further comprising flanges having second planar surfaces;

coupling first planar surfaces of the bone screw with second planar surfaces of the bushing to thereby restrict movement of the bone screw to a single plane;

providing a housing having an upper portion, a lower portion and a first axis extending between the upper and lower portions, the housing having a first opening at the upper portion and a second opening at the lower portion, the housing further comprising an inner groove for receiving the shoulder of the bushing;

delivering the bone screw and bushing into the housing; and

rotating the bushing until the shoulder of the bushing is received in a groove of the housing,

wherein delivering comprises drop-loading the bone screw downwardly into the housing, followed by drop-loading the bushing into the housing on top of the bone screw.

16. The method of claim 15 , wherein delivering comprises drop-loading the bone screw and bushing downwardly together into the housing.

Assignments (15)